Re: [IPv6] Something I don't understand

[RVP <rvp%SDF.ORG@localhost>]

On Fri, 8 Sep 2023, BERTRAND Joël wrote:

> 	Now, both Linux and NetBSD can send and receive IPv6 packets but
> workstations on LAN cannot use IPv6 through NetBSD server.

OK, so both legendre and rayleigh can ping6 the outside world?

> as my ISP routes PREFIX:a00::/56 network
>
> 	When I try a ping6 www.google.fr from LAN, NetBSD's wan interface sends:
>
> 09:38:32.261784 IP6 PREFIX:a10:d65d:64ff:feb4:9a3b >
> par10s21-in-x03.1e100.net: ICMP6, echo request, seq 1, length 64
> 09:38:33.277892 IP6 PREFIX:a10:d65d:64ff:feb4:9a3b >
> par10s21-in-x03.1e100.net: ICMP6, echo request, seq 2, length 64

So, if ICMP packets from the LAN are going out of your gateway
machine to the ISP, I would say your internal routing is fine. You
should've seen a reply because now the sending of those ICMP packets
and the routing of the replies are your ISPs responsibility. Your
part is done.

> 	I suppose NetBSD cannot route ICMP6 answer as www.google.fr sends its
> answer to PREFIX:a10:d65d:64ff:feb4:9a3b and WAN address is
> PREFIX:a00::/64 (PREFIX:a10::/64 is only on LAN side).

PREFIX:a00::/56 is "wider" than PREFIX:a00::/64 or PREFIX:a10::/64,
and since your ISP will (or should!) send all packets destined for
PREFIX:a00::/56 to legendre, ICMP replies to requests from LAN
hosts should also be seen on wm2.

> How can I configure WAN interface to accept IPv6 packets for LAN ?

You can't--your ISP should routing this (ie. the whole of
PREFIX:a00::/56) for you.

You say only legendre and rayleigh work OK. Can you do this:

Install a ping app on your smartphone. Then ping legendre, rayleigh
and some other machines on the LAN (make sure to use the cellular
network rather than your local WiFi connection!). Do a tcpdump on
legendre/wm3. See what packets arrive and which doesn't. Also try
out a bunch of IPv6 addresses in the range assigned to you, even
if they're not assigned to any of your machines. You should see
all of them on the gateway machine.

-RVP